Two H.264 MP4 files, close one to another. The files are playable, a sort of: Windows desktop players (except Media Foundation based), QuickTime, Android and iOS devices play them. The files are not flawless but make sense, hence the glitches.
There is a problem with the second file, which is rejected by Twitter “Your media file could not be processed.”. The file is treated well by browser, and uploaded to remote server. Twitter is unable to convert it on its backend.